Powdered milk, method for manufacturing solid milk, solid milk, and method for measuring average sphericity of powder

Abstract

Provided are powdered milk having excellent compactibility, a method for manufacturing solid milk using the same, and solid milk. In addition, the present invention provides a method for measuring average sphericity of powder in which fine particles are aggregated, in which shape analysis of the powder can be performed. A powdered milk 1 according to the present embodiment has average sphericity Φave of 0.66 or less. Thus, the present embodiment can provide the powdered milk 1 having excellent compactibility.

Description

POWDERED MILK, METHOD FOR MANUFACTURING SOLID MILK, SOLID MILK, AND METHOD FOR MEASURING AVERAGE SPHERICITY OF POWDER

[0001] The present invention relates to powdered milk, a method for manufacturing solid milk, solid milk, and a method for measuring average sphericity of powder.

[0002] The powdered milk is, for example, powder manufactured by removing moisture from milk. In recent years, as solid food, solid milk obtained by compression molding and solidifying powdered milk is known (see, for example, Patent Literature 1). By solidifying the powdered milk in this manner, a shape thereof can be maintained, and a user can easily hold the powdered milk even when the powdered milk is of a powder material.

[0003] Patent Literature 1: JP4062357B

[0004] In the manufacture of such solid milk, it is desired to develop powdered milk excellent in compactibility. In addition, in order to analyze whether the powdered milk is excellent in compactibility, it is also important to analyze the shape of the powdered milk. The shape analysis is a technique to be focused on not only for the powdered milk but also for powder in which fine particles are aggregated similarly to the powdered milk.

[0005] The present invention has been made in view of the above problem, and an object of the present invention is to provide powdered milk having excellent compactibility, a method for manufacturing solid milk using the same, and solid milk. Another object of the present invention is to provide a method for measuring average sphericity of powder in which fine particles are aggregated, in which shape analysis of the powder can be performed.

[0006] The powdered milk according to the present invention has average sphericity of 0.66 or less.

[0007] The method for manufacturing solid milk according to the present invention includes a compression step of compression molding the powdered milk having average sphericity of 0.66 or less to manufacture the solid milk.

[0008] The solid milk according to the present invention is the solid milk manufactured by the above-described manufacturing method, and has tensile strength of 90 [kPa] or more or porosity of 30 [%] or more.

[0009] The method for measuring average sphericity of powder according to the present invention includes: an image acquisition step of acquiring a three-dimensional image obtained by imaging each particle constituting the powder; a three-dimensional model creation step of creating a three-dimensional model of the particle constituting the powder based on the three-dimensional image; and an average sphericity calculation step of calculating average sphericity of the powder based on the three-dimensional model of the particle constituting the powder.

[0010] According to the present invention, it is possible to provide powdered milk having excellent compactibility, a method for manufacturing solid milk using the same, and solid milk. In addition, it is possible to provide a method for measuring average sphericity of powder in which fine particles are aggregated, in which shape analysis of the powder can be performed.

[0011] Fig. 1 is an X-ray CT image obtained by imaging powdered milk according to the present embodiment with an X-ray CT device.Fig. 2 is a flowchart showing a procedure of an average sphericity calculation process.Fig. 3 shows a three-dimensional model of the generated powdered milk.4A of Fig. 4 is a graph showing a relation between a granulation time and average sphericity, and 4B of Fig. 4 is a graph showing a relation between porosity and tensile strength in Examples 1 to 3 and Comparative Example 1.5A of Fig. 5 is a graph showing average sphericity of Examples 4 to 9, and 5B of Fig. 5 is a graph showing average sphericity of Comparative Examples 2 to 16.Fig. 6 is a graph showing a relation between the porosity and the tensile strength in Examples 4 to 9 and Comparative Examples 2 to 16.Fig. 7 is a graph showing a relation between the average sphericity and a compactibility index.

[0012] Hereinafter, embodiments of the present invention will be described. In the following description, the same components as those described above are denoted by the same reference numerals, and the description thereof will be omitted.

[0013] (1) Configuration of Powdered Milk (1-1) Overview of Powdered Milk Fig. 1 is an X-ray computed tomography (CT) image obtained by imaging powdered milk according to the present embodiment with an X-ray CT device. As shown in Fig. 1, powdered milk 1 according to the present embodiment is powder consisting of particles. The powdered milk 1 has irregularities formed by bonding fine spherical particles, elliptical particles, or the like, and has an irregular outer shape as a whole.

[0014] An average particle diameter of the particles constituting the powdered milk 1 according to the present embodiment is about 100 (μm) to 500 (μm). The average particle diameter of the powdered milk 1 can be measured by a laser diffraction particle diameter distribution analyzer (Mastersizer 3000 (manufactured by Malvern Instruments Ltd.)).

[0015] The powdered milk 1 according to the present embodiment can be solidified by compression molding to manufacture solid milk. The solid milk has a large number of voids (for example, pores) generated when the powdered milk 1 as a raw material is compression molded. The plurality of voids are preferably uniformly dispersed (distributed) in the solid milk, and accordingly, the solid milk can be dissolved without any bias and solubility of the solid milk can be increased.

[0016] The solid milk preferably has tensile strength of 90 (kPa) or more as measured by a measurement method described in "(3-2) Relation between Porosity of Molded Body and Tensile Strength of Molded Body" to be described later. When the tensile strength of the solid milk is set to 90 (kPa) or more, strength can be imparted to the solid milk, and the solid milk can be prevented from cracking or chipping. In addition, when the tensile strength of the solid milk is set to 120 (kPa) or more, it is possible to further prevent the solid milk from cracking or chipping due to an external force generated during transportation or the like. Further, when the tensile strength of the solid milk is set to 150 (kPa) or more, resistance to the external force generated during transportation or the like is further improved, and occurrence of cracking or chipping in the solid milk can be further reliably prevented.

[0017] In addition, the solid milk preferably has tensile strength of 300 (kPa) or less as measured by the measurement method described in "(3-2) Relation between Porosity of Molded Body and Tensile Strength of Molded Body" to be described later. When the tensile strength of the solid milk is set to 300 (kPa) or less, a reduction in solubility and disintegrability can be prevented, and when the tensile strength is set to 250 (kPa) or less, the reduction in solubility and disintegrability can be further prevented.

[0018] As described above, the tensile strength of the solid milk is preferably 90 (kPa) or more and 300 (kPa) or less, and further preferably 150 (kPa) or more and 250 (kPa) or less. In addition, the tensile strength of the solid milk is also preferably 90 (kPa) or more and 250 (kPa) or less, and also preferably 150 (kPa) or more and 300 (kPa) or less. In order to impart optimum strength, and optimum solubility and optimum disintegrability to the solid milk depending on a conveyance condition and a use condition, it is preferable to select any of the above-described ranges of the tensile strength.

[0019] Even when the porosity of the solid milk as measured by the measurement method described in "(3-2) Relation between Porosity of Molded Body and Tensile Strength of Molded Body" to be described later is set to 30 (%) or more, the reduction in solubility and disintegrability can be prevented. Further, when the porosity of the solid milk is set to 35 (%) or more and 40 (%) or more, the reduction in solubility and disintegrability can be further prevented, and optimum solubility and disintegrability can be realized according to a use application. In addition, when the porosity of the solid milk is set to 50 (%) or less, strength can be imparted to the solid milk, and the solid milk can be prevented from cracking or chipping. Further, when the porosity of the solid milk is set to 45 (%) or less, it is possible to further prevent the solid milk from cracking or chipping due to an external force generated during transportation or the like.

[0020] As described above, the porosity of the solid milk is preferably 30 (%) or more and 50 (%) or less, and further preferably 30 (%) or more and 45 (%) or less. In addition, the porosity of the solid milk is preferably 35 (%) or more and 50 (%) or less, and further preferably 35 (%) or more and 45 (%) or less. Further, the porosity of the solid milk is preferably 40 (%) or more and 50 (%) or less, and further preferably 40 (%) or more and 45 (%) or less. In order to impart optimum strength, and optimum solubility and disintegrability to the solid milk depending on a conveyance condition and a use condition, it is preferable to select any of the above-described ranges of the porosity.

[0021] The powdered milk 1 according to the present embodiment is the powdered milk 1 for use in a method for manufacturing the solid milk that is solidified by compression molding. Further, the powdered milk 1 according to the present embodiment is used for use in the manufacture of the solid milk that is solidified by compression molding.

[0022] (1-2) Raw Material for Powdered Milk The powdered milk 1 is manufactured from milk in a form of liquid (liquid milk) containing a milk component (for example, component of milk). Examples of the milk component include raw milk (whole fat milk), defatted milk, and cream. A moisture content of the liquid milk is 40 (wt%) to 95 (wt%), for example. A moisture content of the powdered milk 1 is 1 (wt%) to 4 (wt%), for example. A nutritional component to be described later may be added to the powdered milk 1. The powdered milk 1 may be whole powdered milk, defatted powdered milk, or creamy powder. A fat content of the powdered milk 1 is preferably 5 (wt%) to 70 (wt%), for example.

[0023] The milk component as a raw material of the powdered milk 1 is derived from raw milk, for example. Specifically, the milk component is derived from raw milk of such as a cow (Holstein caw, Jersey caw, and the like), a goat, a sheep, and a buffalo. Although the raw milk contains fat, the raw milk may be milk in which a fat content is adjusted by removing a part or all of the fat by centrifugation or the like.

[0024] Further, the milk component as a raw material of the powdered milk 1 is plant milk derived from plant, for example. Specifically, the milk component is derived from plant milk such as soybean milk, rice milk, coconut milk, almond milk, hemp milk, peanut milk, and the like. Although the plant milk contains fat, the plant milk may be milk in which a fat content is adjusted by removing a part or all of the fat by centrifugation or the like.

[0025] Examples of the nutritional component as a raw material of the powdered milk 1 include fat, protein, sugar, mineral, and vitamin, in addition to the milk component. One or two or more of these may be added.

[0026] Examples of the protein that can be a raw material of the powdered milk 1 include milk protein, milk protein fraction, animal protein, vegetable protein, and peptides and amino acids obtained by degrading these protein into various chain lengths with an enzyme or the like. One or two or more of these may be added. Examples of the milk protein include casein and whey protein (α-lactalbumin, β-lactoglobulin, and the like), and examples of the milk protein fraction include whey protein concentrate (WPC) and whey protein isolate (WPI). Examples of the animal protein include egg protein. Examples of the vegetable protein include soybean protein and wheat protein. Examples of the amino acid include taurine, cysteine, cystine, arginine, and glutamine.

[0027] The fat (oil and fat) that can be a raw material of the powdered milk 1 is animal oil and fat, vegetable oil and fat, fractionated oil thereof, hydrogenated oil, and transesterified oil. One or two or more of these may be added. Examples of the animal oil and fat include milk fat, lard, beef tallow, and fish oil. Examples of the vegetable oil and fat include soybean oil, rapeseed oil, corn oil, coconut oil, palm oil, palm kernel oil, safflower oil, cottonseed oil, linseed oil, and medium chain triglyceride (MCT, medium chain fatty acid triglyceride) oil.

[0028] Examples of the sugar that can be a raw material of the powdered milk 1 include oligosaccharides, monosaccharides, polysaccharides, and artificial sweeteners. One or two or more of these may be added. Examples of the oligosaccharide include lactose, sucrose, maltose, galactooligosaccharide, fructooligosaccharide, and lactulose. Examples of the monosaccharide include glucose, fructose, and galactose. Examples of the polysaccharides include starch, soluble polysaccharides, and dextrin. A non-sugar artificial sweetener may be used instead of or in addition to the sugar artificial sweetener.

[0029] Examples of the mineral that can be a raw material of the powdered milk 1 include sodium, potassium, calcium, magnesium, iron, copper, and zinc. One or two or more of these may be added. One or both of a phosphorus compound and a chlorine compound may be used instead of or in addition to the minerals of sodium, potassium, calcium, magnesium, iron, copper, and zinc.

[0030] (1-3) Average Sphericity Average sphericity of the powdered milk 1 is preferably 0.66 or less. The sphericity is one of "shape constants" that define a shape of an object, and is an index indicates that as a value thereof approaches 1 the object becomes closer to a true sphere. When the average sphericity of the powdered milk 1 is set to 0.66 or less, solid milk having excellent compactibility during manufacture of the solid milk and having both appropriate hardness (strength) and appropriate porosity can be manufactured. That is, when the average sphericity of the powdered milk is set to 0.66 or less, contact points and a non-contact area between the powdered milk are increased when the powdered milk 1 is compression molded due to unevenness formed on a surface of each powdered milk, and excellent compactibility (appropriate hardness and appropriate porosity) can be realized. When the number of contact points between the powdered milk 1 increases, contact occurs at many points, and thus a contact area of one contact point is reduced.

[0031] The average sphericity of the powdered milk 1 is more preferably 0.60 or less, further preferably 0.55 or less, and most preferably 0.50 or less. When the average sphericity of the powdered milk 1 is set to 0.60 or less, 0.55 or less, and further 0.50 or less, the contact points and the non-contact area between the powdered milk are increased when the powdered milk 1 is compression molded, and further excellent compactibility can be realized.

[0032] The average sphericity of the powdered milk 1 is preferably 0.10 or more. When the average sphericity of the powdered milk 1 is set to 0.10 or more, it is possible to reduce a load during manufacture, such as reducing a size of a drying equipment used during manufacture, or shortening a time required for granulation. In addition, the average sphericity of the powdered milk 1 is more preferably 0.24 or more, further preferably 0.30 or more, still further preferably 0.36 or more, and most preferably 0.45 or more. When the average sphericity of the powdered milk 1 is set to 0.24 or more, 0.30 or more, 0.36 or more, and further 0.45 or more, the load during manufacture can be further reduced, such as being possible to further shorten the time required for granulation.

[0033] As described above, the average sphericity of the powdered milk 1 is preferably 0.01 or more and 0.66 or less, and further, is also preferably 0.01 or more and 0.60 or less, also preferably 0.01 or more and 0.55 or less, and also preferably 0.01 or more and 0.50 or less. In addition, the average sphericity of the powdered milk 1 is preferably 0.24 or more and 0.66 or less, and further, is also preferably 0.24 or more and 0.60 or less, also preferably 0.24 or more and 0.55 or less, and also preferably 0.24 or more and 0.50 or less. In addition, the average sphericity of the powdered milk 1 is preferably 0.30 or more and 0.66 or less, and further, is also preferably 0.30 or more and 0.60 or less, also preferably 0.30 or more and 0.55 or less, and also preferably 0.30 or more and 0.50 or less.

[0034] In addition, the average sphericity of the powdered milk 1 is preferably 0.36 or more and 0.66 or less, and further, is also preferably 0.36 or more and 0.60 or less, also preferably 0.36 or more and 0.55 or less, and also preferably 0.36 or more and 0.50 or less. In addition, the average sphericity of the powdered milk 1 is preferably 0.45 or more and 0.66 or less, and further, is also preferably 0.45 or more and 0.60 or less, also preferably 0.45 or more and 0.55 or less, and also preferably 0.45 or more and 0.50 or less. For the powdered milk 1, it is preferable to select any of the above-described ranges of the average sphericity according to a situation of a manufacturing equipment or a degree of load reduction during manufacture.

[0035] Next, a procedure of an average sphericity calculation process for calculating the average sphericity of the powdered milk 1 will be described. Fig. 2 is a flowchart showing the procedure of the average sphericity calculation process. Here, in order to measure the average sphericity of the powdered milk 1, a three-dimensional shape of each of the particles constituting the powdered milk 1 is grasped, and a surface area of a particle surface is detected. In the procedure of the average sphericity calculation process, first, in step S1, a total weight w1 (mg) of a predetermined number (n) of particles constituting the powdered milk 1 is measured by a weight scale (total weight measurement step). In step S1, the powdered milk 1 is loosely filled in a polyimide tube of Φ2.5 (mm) to a height of about 2 (mm), and the total weight w1 of the powdered milk 1 in the tube is measured by the weight scale. Here, it is assumed that the total weight w1 of the powdered milk 1 charged into the tube of Φ2.5 (mm) × 2 (mm) is, for example, about 5 (mg).

[0036] Next, in step S2, a particle density ρ (kg / m3) of the predetermined number (n) of particles and a true density ρt (kg / m3) of the particles are measured (particle density and true density measurement step). The particle density ρ is preferably measured using a particle density measuring device "Accupyc II 1345 (manufactured by Shimadzu Corporation)". The particle density ρ is a density including an internal void of the particle. The true density ρt is a density in which only a volume occupied by the particle itself is a volume for density calculation. The true density ρt can be measured by crushing the particles.

[0037] Next, in step S3, an arithmetic processing device acquires a plurality of X-ray CT images obtained by imaging the predetermined number (n) of particles (image acquisition step). In step S3, an internal structure of each particle of the powdered milk 1 (powder) in the tube filled in the above-described tube is imaged using an X-ray CT device (manufactured by Rigaku Corporation, product name "Nano3DX" (registered trademark)).

[0038] Imaging conditions include using L1080 as an X-ray camera lens of the X-ray CT device, setting a target of an X-ray tube as Mo (molybdenum), setting an imaging range to Φ3.6 (mm) × H2.8 (mm), setting binning to 3, setting a resolution (spatial resolution) to 3.3 (μm / voxel), and setting an exposure time to 4 (sec). In step S3, a plurality of (for example, 600) X-ray CT images obtained by imaging the powdered milk 1 in the tube from various angles under the above-described imaging conditions are acquired, and the process proceeds to the next step S4. Here, for example, in a case where a height direction of the tube into which the powdered milk 1 is charged is set as a z axis, one direction of an in-plane direction orthogonal to the z axis of the tube is set as an x axis, and a direction orthogonal to each of the x axis and the z axis of the in-plane direction is set as a y axis, the powdered milk 1 in the tube is imaged by the X-ray CT device from various angles, and X-ray CT images in which a density is indicated by luminance information for each of the x axis, y axis, and z axis coordinates in the tube are obtained. The arithmetic processing device can generate a three-dimensional image representing the powdered milk 1 in a three-dimensional manner from the plurality of X-ray CT images. Hereinafter, the term "X-ray CT image" also includes the three-dimensional image generated from the plurality of X-ray CT images.

[0039] Next, in step S4, a binarization threshold value when each of the obtained plurality of X-ray CT images in which the predetermined number of particles are imaged is to be binarized by the arithmetic processing device is assumed (threshold value setting step). The binarization threshold value for the X-ray CT image is a threshold value for distinguishing a contour shape of each particle, a gap between adjacent particles, and an internal void of each particle. The arithmetic processing device is a computer that can execute arithmetic processing, image processing such as binarization processing, and the like. Next, in step S5, the arithmetic processing device acquires a binarized image of the predetermined number of particles obtained by binarizing the X-ray CT image with the set binarization threshold value (binarized image acquisition step), and the process proceeds to the next step S6.

[0040] In step S6, the arithmetic processing device determines whether a theoretical total volume v1 (m3) of the predetermined number (n) of particles calculated based on the total weight w1 of the powdered milk 1 in the tube and the true density of the particles is equal to a total volume v2 (m3) of the predetermined number of particles in the binarized image (volume determination step). The theoretical total volume v1 of the predetermined number of particles is calculated by total weight w1 / true density ρt. The total volume v2 of the predetermined number of particles in the binarized image is calculated, for example, based on the predetermined number of particles identified from the binarized image by image processing.

[0041] Here, if the binarization threshold value when the X-ray CT image is binarized in step S5 is an appropriate value, the theoretical total volume v1 is equal to the total volume v2. On the other hand, if the binarization threshold value when the X-ray CT image is binarized in step S5 is not an appropriate value, the theoretical total volume v1 is not equal to the total volume v2.

[0042] When a negative result is obtained in step S6, this indicates that the theoretical total volume v1 is not equal to the total volume v2, and in this case, the arithmetic processing device proceeds to the next step S7. In step S7, the arithmetic processing device corrects the threshold value when the X-ray CT image is binarized in step S5 (threshold value correction step), and returns to step S5 again. In a case where the total volume v2 is greater than the theoretical total volume v1, the binarization threshold value is corrected in a direction in which the total volume v2 is reduced. In addition, in a case where the total volume v2 is smaller than the theoretical total volume v1, the binarization threshold value is corrected in a direction in which the total volume v2 is increased. The correction of the binarization threshold value may be performed by correcting the threshold value to any value by a user, or by automatically correcting the value of the threshold value at predetermined intervals by the arithmetic processing device. In step S5, the arithmetic processing device binarizes the X-ray CT image with the threshold value corrected in step S7, and acquires a binarized image of the predetermined number of particles. Thereafter, until a positive result is obtained in step S6, the binarization threshold value is corrected and the above-described processes are repeated.

[0043] On the other hand, when a positive result is obtained in step S6, this indicates that the theoretical total volume v1 is equal to the total volume v2, and in this case, the arithmetic processing device proceeds to the next step S8. In step S8, the arithmetic processing device assumes a maximum internal void volume v3 (m3) (void volume setting step). The maximum internal void volume v3 is a volume of an internal void having the largest volume among a plurality of internal voids present in one particle, and can be assumed by domain knowledge or the like.

[0044] Next, in step S9, the arithmetic processing device fills an internal void having the maximum internal void volume v3 or less among the internal voids present inside each of the predetermined number of particles specified in the binarized image by image processing, and the proceeds to the next step S10. For example, in the binarized image, a solid portion of the particle is represented in white, and the internal void inside the particle is represented in black (color different from color of solid portion). In this case, the arithmetic processing device generates a binarized image in which a black region having the maximum internal void volume v3 or less among black regions indicating internal voids in a display region of the predetermined number of particles in the binarized image is filled with white, and internal voids inside the particles having the maximum internal void volume v3 or less are filled and removed by image processing.

[0045] In step S10, the arithmetic processing device determines whether internal porosity ε1 of the entire predetermined number of particles calculated based on the true density ρt of the particles and the particle density ρ of the particles is equal to internal porosity (hereinafter, also referred to as estimated internal porosity) ε2 of the entire predetermined number of particles obtained based on the binarized image in which the internal voids are removed based on the maximum internal void volume v3 in step S9 (porosity determination step). The estimated internal porosity ε2 can be obtained by performing image analysis on the binarized image by the arithmetic processing device.

[0046] When a negative result is obtained in step S10, this indicates that the internal porosity ε1 calculated based on the true density ρt of the particles and the particle density ρ of the particles is not equal to the estimated internal porosity ε2 of the binarized image, and in this case, the arithmetic processing device proceeds to the next step S11.

[0047] In step S11, the arithmetic processing device corrects the maximum internal void volume v3 serving as a reference for filling internal voids in step S9, and returns to step S9 again (void volume correction step). In a case where the estimated internal porosity ε2 is greater than the internal porosity ε1, the value of the maximum internal void volume v3 is corrected in a direction in which the estimated internal porosity ε2 is reduced. In addition, in a case where the estimated internal porosity ε2 is smaller than the internal porosity ε1, the value of the maximum internal void volume v3 is corrected in a direction in which the estimated internal porosity ε2 is increased. The correction of the maximum internal void volume v3 may be performed by correcting the maximum internal void volume v3 to any value by a user, or by automatically correcting the value of the maximum internal void volume v3 at predetermined intervals by the arithmetic processing device. In step S9, the arithmetic processing device fills internal voids surrounded by an outline of the particle having the maximum internal void volume v3 or less corrected in step S11. Thereafter, until a positive result is obtained in step S10, the maximum internal void volume v3 is corrected and the above-described processes are repeated.

[0048] On the other hand, when a positive result is obtained in step S10, this indicates that the internal porosity ε1 calculated based on the true density ρt of the particles and the particle density ρ of the particles is equal to the estimated internal porosity ε2 of the binarized image, and in this case, the arithmetic processing device proceeds to the next step S12.

[0049] In step S12, the arithmetic processing device creates a three-dimensional model of a predetermined number of particles based on a binarized image of the predetermined number of particles (three-dimensional model creation step). In this case, in step S12, the arithmetic processing device converts a voxel model of each particle, which is volume data and represented by a large number of voxels in the binarized image, into a polygon model using a marching cube method to create a predetermined number (n) of three-dimensional models. Fig. 3 shows an example of one of the generated three-dimensional models of the powdered milk 1.

[0050] The three-dimensional model is a polygon model of a three-dimensional structure having information on volume and area, and is different from a three-dimensional X-ray CT image which is an aggregate of a plurality of images having information on height direction. Even in a case of two-dimensional imaging data, for example, by assuming that trapezoidal approximation can be performed between two images, it is possible to extract the information on volume and area by integrating data without creating a three-dimensional model. On the other hand, in such a two-dimensional approximation calculation, in a case where curvature of the powder is high or anisotropy of the powder is high, the information on area and volume varies depending on an orientation of a two-dimensional image, and a shape thereof may not be accurately extracted.

[0051] The three-dimensional model is shape information extracted from all scalar information of three-dimensionally distributed adjacent voxels, and can accurately extract shape information such as a volume or an area as compared to a method for mathematically performing trapezoidal approximation of shape information from one-dimensional adjacent information in one direction, and thus the three-dimensional model is suitable for measurement of sphericity that can be used to measure a complicated particle form.

[0052] In step S12, in the case where the three-dimensional model of the predetermined number of particles is created based on the binarized image of the predetermined number of particles, for example, in a case where the three-dimensional model which is a polygon has a constricted portion having an area A (for example, 100 (μm2)) or less, it is preferable to recognize that the polygon is another particle from the constricted portion. The area A of the constricted portion in which the polygon is distinguished as another particle is adjusted such that, for example, a three-dimensional model generated by distinguishing the polygon as another particle from the constricted portion and separating the polygon becomes a three-dimensional model equal to a median diameter calculated by a laser diffraction particle diameter distribution analyzer (Mastersizer 3000 (manufactured by Malvern Instruments Ltd.)).

[0053] Next, in step S13, the arithmetic processing device calculates, from the three-dimensional image, a volume Vi and a surface area Si of a predetermined number (n) of three-dimensional models i (i is an identifier of the three-dimensional model and is an integer of 1 to n) from which internal voids are removed, respectively. For example, in step S13, the arithmetic processing device calculates average sphericity Φave, which is average sphericity of the predetermined number (n) of three-dimensional models i, according to the following formula (1) based on the calculated volume Vi and surface area Si of the three-dimensional model i (average sphericity calculation step), and ends the above-described procedure of the average sphericity calculation process.

[0054]

[0055] As described above, in the present embodiment, the binarization processing is performed on the X-ray CT image, each particle laminated in the X-ray CT image is specified, and the three-dimensional model is generated for each specified particle using the marching cube method. When the binarization processing is performed, in order to prevent an error from being included during processing executed by the marching cube method due to the binarization processing (for example, in order to prevent a three-dimensional model from being generated by identifying a plurality of particles as one particle), it is preferable to set the threshold value during the binarization processing and the maximum internal void volume v3 to optimum values. Accordingly, a three-dimensional model in which a shape of each particle is accurately reproduced can be created based on the binarized image generated based on the X-ray CT image.

[0056] In the X-ray CT image obtained by imaging the powdered milk 1, since a density difference between air and the powdered milk 1 is extremely large, it is easy to detect a boundary surface between a gas and a solid, and it can be said that a large difference does not occur in a measurement result depending on a condition during measurement when detecting the presence or absence of an object.

[0057] Here, in a case where the resolution of the X-ray CT device is greatly changed, an error may occur in a value of the sphericity of the powdered milk 1. When the resolution is greatly changed, finer undulations of the powdered milk 1 are observed, and thus an area value is increased. Therefore, it is considered that when the resolution is 1 / 150 or more and 1 / 30 or less of the average particle diameter of the powdered milk 1 (about 2 μm to 10 μm), the sphericity can be measured with almost no error. The average particle diameter of the powdered milk 1 is determined by a laser diffraction particle diameter distribution analyzer (Mastersizer 3000 (manufactured by Malvern Instruments Ltd.)). For example, in a case where the powdered milk 1 has an average particle diameter of about 100 (μm), the average sphericity can be obtained based on an X-ray CT image obtained at a resolution of 1.1 (μm). Alternatively, in a case where the powdered milk 1 has an average particle diameter of about 100-500(μm), the average sphericity can be obtained based on an X-ray CT image obtained at a resolution of 3.3 (μm).

[0058] In a case where the powdered milk 1 is imaged at a resolution of less than 1 / 150 of the average particle diameter of the powdered milk 1, not only a shape of the entire powdered milk 1 but also very micro surface roughness may be measured in the X-ray CT image, and an error may occur. On the other hand, in a case where the powdered milk 1 is imaged at a resolution of more than 1 / 30 of the average particle diameter, the shape (boundary surface between gas and solid) of the powdered milk 1 may not be accurately reproduced, and thus it is expected that the polygon is simplified and a numerical value is deviated. Therefore, the resolution is preferably 1 / 150 to 1 / 30 of the average particle diameter.

[0059] (1-4) Density The particle density ρ of the powdered milk 1 is preferably 1.16 (g / cm3) or less, and more preferably 1.15 (g / cm3) or less. The particle density ρ is preferably measured using a particle density measuring device "Accupyc II 1345 (manufactured by Shimadzu Corporation)". The particle density ρ is a density including an internal void of the powdered milk 1. When the particles have a constant true density ρt, the particle density ρ is a parameter that changes depending on the internal void of the powdered milk 1, and is an index that more directly affects the compactibility (porosity and strength of solid milk). The powdered milk 1 can realize good compression compactibility when the particle density ρ is set to 1.16 (g / cm3) or less, and can realize further good compression compactibility when the particle density ρ is set to 1.15 (g / cm3) or less.

[0060] The particle density ρ of the powdered milk 1 is preferably 1.08 (g / cm3) or more, more preferably 1.10 (g / cm3) or more, and further preferably 1.14 (g / cm3) or more. When the particle density ρ of the powdered milk 1 is set to 1.08 (g / cm3) or more, the strength of the particles can be ensured, and wear after solidification can be prevented. In addition, when the particle density ρ of the powdered milk 1 is set to 1.10 (g / cm3) or more, and further to 1.14 (g / cm3) or more, the strength of the particles can be further ensured, and the wear after solidification can be further prevented.

[0061] As described above, it is preferable that the average sphericity Φave of the powdered milk 1 is set to 0.66 or less, and the particle density ρ of the powdered milk 1 is set to 1.08 (g / cm3) or more and 1.16 (g / cm3) or less, and further 1.08 (g / cm3) or more and 1.15 (g / cm3) or less. In addition, it is preferable that the average sphericity Φave of the powdered milk 1 is set to 0.66 or less, and the particle density ρ of the powdered milk 1 is set to 1.10 (g / cm3) or more and 1.16 (g / cm3) or less, and further 1.10 (g / cm3) or more and 1.15 (g / cm3) or less. Further, it is preferable that the average sphericity Φave of the powdered milk 1 is set to 0.66 or less, and the particle density ρ of the powdered milk 1 is set to 1.14 (g / cm3) or more and 1.16 (g / cm3) or less, and further 1.14 (g / cm3) or more and 1.15 (g / cm3) or less. For example, by adjusting the powdered milk 1 to satisfy any of the numerical ranges described above, more preferable solid milk having excellent compression compactibility during manufacture of the solid milk and having both appropriate hardness and appropriate solubility can be manufactured.

[0062] (1-5) Uniformity Uniformity of the powdered milk 1 is preferably 0.60 or less. The uniformity is one of values defining properties of the particles, and is an index indicating that the smaller the value, the more uniform the particle diameter. When the uniformity of the powdered milk 1 is set to 0.60 or less, solid milk having excellent compactibility during manufacture of the solid milk and having both appropriate hardness (strength) and appropriate porosity can be manufactured.

[0063] In addition, the uniformity of the powdered milk 1 is more preferably 0.60 or less, preferably 0.55 or less, further preferably 0.45 or less, and most preferably 0.40 or less. When the particles are uniform, solid milk having both appropriate hardness (strength) and appropriate porosity can be manufactured.

[0064] The uniformity of the powdered milk 1 is more preferably 0.40 or more, preferably 0.3 or more, and most preferably 0.25 or more. By setting the uniformity to these values, the load during manufacture can be further reduced such as capable of shortening the time required for granulation.

[0065] As described above, the uniformity of the powdered milk 1 is preferably 0.25 or more and 0.6 or less, and further preferably 0.25 to 0.45. This is because solid milk having excellent compactibility during manufacture of the solid milk and having both appropriate hardness (strength) and appropriate porosity can be manufactured.

[0066] In addition, when the uniformity of the powdered milk 1 is set to 0.4 or more and 0.6 or less, it is possible to reduce the load during manufacture such as shortening the time required for granulation, and simplifying classification equipment and sizing equipment.

[0067] The uniformity can be calculated by the following method. (1-5-1) A difference is calculated by subtracting the particle diameter from the median diameter of the particles (value of the particle diameter corresponding to 50% of particle diameter distribution). (1-5-2) An absolute value of the difference calculated in the above-described "(1-5-1)" is multiplied by a frequency of the particle diameter in the particle diameter distribution to calculate a value. (1-5-3) For each particle diameter obtained in the particle diameter distribution, the above-described "(1-5-1)" and "(1-5-2)" are performed, and then a sum of values in "(1-5-2)" of all particles is calculated. (1-5-4) The value calculated in the above-described "(1-5-3)" is divided by a value obtained by multiplying the median diameter by a sum of frequencies of the particle diameter distribution (usually 1). The value calculated in (1-5-4) is the uniformity. The particle diameter, the frequency, and the like can be measured by a known laser diffraction particle diameter distribution analyzer or the like.

[0068] (2) Method for Manufacturing Powdered Milk Next, a method for manufacturing the powdered milk 1 will be described. The powdered milk 1 according to the present embodiment can be manufactured by a powdered milk manufacturing step, and the powdered milk manufacturing step preferably includes, for example, a liquid milk preparation step, a liquid milk clarification step, a sterilization step, a homogenization step, a concentration step, and a drying step. The liquid milk preparation step is a step of preparing liquid milk of the components described above. The liquid milk clarification step is a step for removing fine foreign matters contained in the liquid milk. In order to remove the foreign matters, for example, a centrifuge, a filter, or the like may be used.

[0069] The sterilization step is a step for killing microorganisms such as bacteria contained in water, milk components, or the like of the liquid milk. Since microorganisms considered to be actually contained therein vary depending on a type of the liquid milk, sterilization conditions (sterilization temperature and holding time) are appropriately set according to the microorganisms.

[0070] The homogenization step is a step for homogenizing the liquid milk. Specifically, a particle diameter of solid components such as fat spheres contained in the liquid milk is reduced, and the solid components are uniformly dispersed in the liquid milk. In order to reduce the particle diameter of the solid components of the liquid milk, for example, the liquid milk may be caused to pass through a narrow gap while being pressurized.

[0071] The concentration step is a step for concentrating the liquid milk. For the concentration of the liquid milk, for example, a vacuum evaporation pan or an evaporator may be used. A concentration condition is appropriately set within a range in which components of the liquid milk are not excessively denatured. Accordingly, concentrated milk can be obtained from the liquid milk.

[0072] The drying step preferably includes a spray drying step of spray drying the liquid milk as a raw material of the powdered milk 1 to obtain the powdered milk 1. In the spray drying step, the liquid milk as a raw material is sprayed, and the sprayed liquid milk is dried to obtain the powdered milk 1. In addition, as the drying step including the spray drying step, for example, a foam drying step can also be used.

[0073] The foam drying step is a step of manufacturing the powdered milk 1 according to a foam drying method. The foam drying method includes a gas dispersion step of dispersing a predetermined gas in the liquid milk as a raw material. In the gas dispersion step, it is preferable that a predetermined gas having a volume of 1×10-2times or more and 7 times or less the volume of the liquid milk is dispersed in the liquid milk. In addition, in the gas dispersion step, it is preferable that the liquid milk is poured along a flow path in a state in which a ratio of a volume flow rate of the predetermined gas to the liquid milk is 1×10-2times or more and 7 times or less. Further, in the gas dispersion step, it is preferable that the predetermined gas is mixed with the liquid milk in a pressurized state. As the gas, one or two or more gases selected from the group consisting of carbon dioxide, air, nitrogen, oxygen, and a rare gas can be applied.

[0074] The foam drying method includes the spray drying step of spraying the liquid milk subjected to the above-described gas dispersion step and drying the sprayed liquid milk to obtain the powdered milk 1. In the spray drying step, the liquid milk in a state in which the predetermined gas is dispersed in the above-described gas dispersion step and a density of the liquid milk is reduced is sprayed. It is preferable that the spray drying step is continuously performed within a period of 0.1 seconds or more and 5 seconds or less after the gas dispersion step is completed.

[0075] In the foam drying method, such gas dispersion step and spray drying step are continuously performed, and the average sphericity Φave of the powdered milk 1 can be adjusted to 0.66 or less by adjusting a degree of dispersion of the gas in the liquid milk, a spray condition of the liquid milk, the number of repetitions of the gas dispersion step and the spray drying step, and the like to bind and dry fine particles (drying step).

[0076] In the above-described manufacturing method, after the concentration step, the drying step of spray drying the liquid milk as the raw material of the powdered milk 1 is performed to manufacture the powdered milk 1 having average sphericity of 0.66 or less, but the present invention is not limited thereto. In addition, the powdered milk 1 can also be manufactured using a granulation step. In a case where the granulation step is used, the powdered milk 1 having average sphericity of 0.66 or less may be manufactured by performing the drying step after the concentration step and further performing the granulation step after the drying step. In addition, the powdered milk 1 having average sphericity of 0.66 or less may be manufactured by simultaneously perform the granulation step in a process of performing the drying step after the concentration step, for example, such as simultaneously performing drying and granulation as in the spray drying, and performing the drying step and the granulation step as the same step without distinction.

[0077] The granulation step is a step of binding the powdered milk 1 to each other using a binder such as a liquid. In the granulation step, a spray dryer, an extrusion granulator, a mixer granulator, a fluidized layer granulator, a fluidized bed granulator, a rolling granulator, a rolling fluidized layer granulator, a dry granulator, or the like may be used. A fluidized layer granulation step is a step of manufacturing the powdered milk 1 according to a fluidized layer granulation method. In the fluidized layer granulation method, granulation is performed by allowing a gas such as heated air to flow into a granulation tank to cause particles to flow by the gas and spraying a liquid onto the particles in a flowing state. In the fluidized layer granulation method, desired powdered milk 1 can be manufactured by binding fine particles with a liquid and drying the fine particles.

[0078] In the fluidized layer granulation method, the average sphericity Φave of the powdered milk 1 can be adjusted to 0.66 or less by adjusting an inflow amount of the heated air flowing into the granulation tank, a degree of dispersion of the gas in the fine particles, a spraying condition of the liquid, a time for rolling and flowing, and the like to mix the fine particles with each other using water without using a binder, and binding and drying the plurality of fine particles (granulation step).

[0079] Then, solid milk can be manufactured by compression molding the powdered milk 1 thus manufactured (compression step).

[0080] Through the above-described steps, the powdered milk 1 having average sphericity Φave suitable for manufacturing the solid milk can be manufactured. Then, the obtained powdered milk 1 is compression molded to form a compression molded body. A shape of the compression molded body is determined by a shape of a die(mortar of tableting machine) used for the compression molding, but is not particularly limited as long as the shape has a certain degree of dimension (size, thickness, and angle). The shape of the compression molded body is a cylindrical shape, an elliptic cylindrical shape, a cubic shape, a rectangular parallelepiped shape, a plate shape, a polygonal columnar shape, a conical shape, a polygonal pyramid shape, a truncated conical shape, a truncated polygonal pyramid shape, a spherical shape, a polyhedral shape, or the like. From the viewpoint of ease of molding, convenience of transportation, and the like, a cylindrical shape, an elliptic cylindrical shape, and a rectangular parallelepiped shape are preferable. Next, the obtained powdered milk compression molded body is subjected to a curing treatment including a humidifying treatment and a drying treatment to manufacture the solid milk.

[0081] In the solid milk manufactured by the above-described manufacturing method, tensile strength can be set within a range of, for example, 90 (kPa) or more and 300 (kPa) or less. In addition, porosity of the solid milk manufactured by the above-described manufacturing method can be set within a range of, for example, 30 (%) or more and 50 (%) or less.

[0082] (3) Verification Test (3-1) Relation between Granulation Time and Sphericity Next, a relation between the granulation time and the sphericity when manufacturing the powdered milk 1 was examined. Here, the powdered milk 1 was manufactured using the fluidized layer granulation method according to the above-described manufacturing method. As a raw material of the powdered milk 1, Meiji FM-T (manufactured by Meiji Co., Ltd.) was used.

[0083] In the fluidized layer granulation method, 800 (g) of fine particles serving as the raw material were charged into a rolling fluidized bed granulator (product name: "Multiplex MP-01", manufactured by powrex corp.), an air supply temperature was set to a normal temperature of 25 (°C), and air was blown at 0.4 (m3 / min). In the rolling fluidized layer granulator, a rotation speed of a rotor was set to 1,000 (rpm), a flow rate of water was set to 1.6 (g / min), and the air was sprayed from a two-fluid nozzle at 36 (NL / min). Then, a granulation time for performing granulation by spraying water to cause fine particles to flow was changed to 0 (min), 10 (min), 20 (min), and 30 (min), and after the lapse of each granulation time, dry heat drying was performed at an exhaust temperature of 98 (°C) to manufacture powdered milk consisting of particles for each granulation time. A drying time was adjusted to be equal to (within ± 0.2 (%)) a moisture value (1.9 (%)) of the original raw material.

[0084] Next, the average sphericity Φave was calculated according to the average sphericity calculation process described in the above-described "(1-3) Average Sphericity" for each powdered milk manufactured with the granulation time being changed. As a result, results as shown in 4A of Fig. 4 were obtained.

[0085] As shown in 4A of Fig. 4, it could be confirmed that the average sphericity Φave is reduced as the granulation time is increased, and irregularities are formed on a particle surface. In addition, it could be confirmed that the powdered milk 1 having average sphericity Φave of 0.66 or less can be manufactured when the granulation time is set to 10 (min) or more.

[0086] (3-2) Relation between Porosity of Molded Body and Tensile Strength of Molded Body Next, considering the powdered milk of which the granulation time was 0 (min) as Comparative Example 1, the powdered milk 1 of which the granulation time was 10 (min) as Example 1, the powdered milk 1 of which the granulation time was 20 (min) as Example 2, and the powdered milk 1 of which the granulation time was 30 (min) as Example 3, a compression molded body (hereinafter, simply referred to as molded body) obtain by forming solid milk from powdered milk was manufactured for each example, and when porosity and tensile strength of the molded body were examined, results as shown in 4B of Fig. 4 were obtained.

[0087] The molded body was manufactured by compression molding each powdered milk of Comparative Example 1 and Examples 1 to 3 under the following compression conditions. In this verification test, in consideration of the fact that a theoretical compression molding behavior does not occur depending on a design such as corners of the molded body and the fact that it is difficult to convert strength of the obtained molded body into a material mechanics physical property value (= strength), an evaluation experiment was performed using the molded body compression molded into a cylindrical tablet shape for which strength conversion is possible.

[0088] In this verification test, 0.694 (g) of a powdered milk sample was filled in a standard die (compression area = 100 (mm2)) having an inner diameter of 11.28 (mm) and compressed at a compression rate of 10 (mm / s) using a tableting simulator (product name: Styl'One (Medel Pharma)). A thickness of the molded body having a cylindrical tablet shape was adjusted by adjusting a punch interval, and the tensile strength of the obtained molded body having a cylindrical tablet shape was measured with a load cell-type tablet hardness tester (portable checker PC-30 (manufactured by Okada Seiko Co., Ltd.)).

[0089] A circular bottom surface of the molded body having a cylindrical tablet shape was placed on a load cell-type tablet hardness tester, a fracture terminal was pressed against a peripheral surface of the molded body at a constant speed, and a load (N) when the molded body fractured was measured.

[0090] A force f(N) applied to a jig by the load cell-type tablet hardness tester when the molded body having a cylindrical tablet shape fractured can be converted into tensile strength σ by the following formula (2) using an Airy stress function. Hereinafter, D represents a diameter (m) of a circular end surface of the molded body having a cylindrical tablet shape, and t represents a height (m) of the molded body having a cylindrical tablet shape in an axial direction. A vertical axis of 4B of Fig. 4 shows the tensile strength σ related to Comparative Example 1 and Examples 1 to 3.

[0091]

[0092] The porosity was calculated as follows. Since it is not easy to obtain the porosity by actually measuring the true density of the powdered milk, the porosity ε was calculated for each of Comparative Example 1 and Examples 1 to 3 by the following formula (3) using 1.12 (g / cm3) which is a representative particle density. In this verification test, since all the compositions are the same, there is no significant problem even when the calculated density is constant. A horizontal axis of 4B of Fig. 4 shows the porosity ε related to Comparative Example 1 and Examples 1 to 3.

[0093]

[0094] It can be said that the molded body has good solubility (ease of dissolving in solvent such as water) when the porosity ε is high, and the molded body is easy to handle when the tensile strength σ is high. It is desired that the molded body has both high porosity ε and high tensile strength σ. From the results of 4A and 4B of Fig. 4, it was confirmed that the tensile strength σ was increased as the average sphericity Φave was reduced, and the compactibility of the molded body was improved as the average sphericity Φave was reduced. Here, the fact that the compactibility is improved means that the tensile strength σ is high even at the same porosity ε. It was confirmed that as compared with Comparative Example 1, the tensile strength σ in Examples 1 to 3 was improved even when the porosity ε was the same, and the compactibility was improved with respect to that in Comparative Example 1.

[0095] (3-3) Comparison with Existing Product Next, powdered milk 1 of Examples 4 to 9 was manufactured using the fluidized layer granulation method in the same manner as in the above-described Examples, and average sphericity Φave of the obtained powdered milk 1 was measured. Results thereof are shown in 5A of Fig. 5. In Examples 4 to 9, the powdered milk 1 was manufactured by performing granulation under different granulation conditions, and all had average sphericity Φave of 0.66 or less. In addition, the uniformity thereof was 0.4 to 0.6.

[0096] Here, in a case where the compactibility of the molded body manufactured from the powdered milk is to be confirmed, since the compactibility is greatly affected when the density is different, powdered milk having a density of 1.155 ± 0.01 (g / ml) was prepared as a sample in this verification test. In addition, since the compactibility is also affected when a moisture value is too high, powdered milk having a moisture value of 1 (wt%) to 4.0 (wt%) was used as the sample. Regarding blending, since the compactibility is affected when a blending ratio of sugars and oils and fats is greatly changed, powdered milk containing 50 (wt%) to 58 (wt%) of sugars and 24 (wt%) to 28 (wt%) of lipids was used as the sample.

[0097] Separately, powdered milk of 15 kinds of existing products was obtained and used as Comparative Examples 2 to 16.

[0098] Comparative Example 2 is Hagukumi (manufactured by MORINAGA MILK INDUSTRY CO., LTD.). Comparative Example 3 is HiQ comfort (manufactured by Nutricia). Comparative Example 4 is Meiji FM-T (manufactured by Meiji Co., Ltd.). Comparative Example 5 is Anmun (manufactured by Fonterra Co-operative Group Limited). Comparative Examples 6 and 7 are Aptamil (manufactured by Danone S.A.). Comparative Example 8 is Jinlingguan Zhenhu (manufactured by YILI.COM INC.). Comparative Example 9 is Fubo Ruimu (manufactured by Synutra.com inc.). Comparative Example 10 is Jingzhi (manufactured by Mengniu Dairy). Comparative Example 11 is NAN (manufactured by Nestle Ltd.). Comparative Example 12 is BELSOL (manufactured by WYETH LLC.). Comparative Example 13 is Frisolac (manufactured by Koninklijke FrieslandCampina N.V.). Comparative Example 14 is Meikegaote Chunguan (manufactured by Mead Johnson). Comparative Example 15 is Nutrilon (manufactured by Nutricia). Comparative Example 16 is Xingfeifan (manufactured by Feihe Dairy Co. Ltd.). Comparative Examples 2 to 16 are powdered milk having a density of 1.18 ± 0.03 (g / ml). A moisture value thereof is 1 (wt%) to 4.0 (wt%). The powdered milk has 50 (wt%) to 58 (wt%) of sugars and 24 (wt%) to 28 (wt%) of lipids in the blending. Comparative Examples 2 to 16 are of the same types of powdered milk as those of Examples 4 to 9.

[0099] Also for Comparative Examples 2 to 16, average sphericity Φave was calculated according to the average sphericity calculation process described in the above-described "(1-3) Average Sphericity", respectively. Results thereof are shown in 5B of Fig. 5. It was confirmed that in all of Comparative Examples 2 to 16, the average sphericity Φave was 0.67 or more. From 5A and 5B of Fig. 5, it can be confirmed that Comparative Examples 2 to 16, which are general powdered milk, have average sphericity Φave of 0.67 or more, and Examples 4 to 9 having average sphericity Φave of 0.66 or less (0.50 or less) are specific powdered milk.

[0100] Next, the powdered milk of Examples 4 to 9 and Comparative Examples 2 to 16 was also compression molded under the same compression conditions as in the above-described "(3-2) Relation between Porosity of Molded Body and Tensile Strength of Molded Body" to manufacture molded bodys, respectively. When the porosity ε and the tensile strength σ of each of the molded bodys of Examples 4 to 9 and Comparative Examples 2 to 16 were examined, results as shown in Fig. 6 were obtained. The results of Examples 4 to 9 are indicated by a solid line, and the results of Comparative Examples 2 to 16 are indicated by a dotted line, a dot dash line, and a one-dot-dash line.

[0101] In Fig. 6, the horizontal axis represents the porosity ε, and the vertical axis represents the tensile strength σ. The porosity ε in Fig. 6 was calculated based on the above formula (3) as in the above-described Examples 1 to 3. The tensile strength σ in Fig. 6 was calculated based on the above formula (2) as in the above-described Examples 1 to 3.

[0102] Based on the results in 5A and 5B of Fig. 5 showing calculation results of the average sphericity Φave and Fig. 6 showing calculation results of the porosity ε and the tensile strength σ, it was confirmed that in Examples 4 to 9 in which the average sphericity Φave was 0.66 or less, the tensile strength σ was improved as compared with that in Comparative Examples 2 to 16 in which the average sphericity Φave was 0.67 or more even when the porosity ε was the same, and the compactibility was improved with respect to that in Comparative Examples 2 to 16.

[0103] (3-4) Relation between Average Sphericity and Compactibility Index Here, based on the results in Fig. 6, the compactibility of the powdered milk can be represented by a straight line having substantially the same slope when the tensile strength σ is plotted on a logarithmic scale. Therefore, experimental values obtained from each sample were approximated by a least squares method using the following formula (4), and the compactibility was evaluated by a compactibility index Ic.

[0104] σ = Ic・exp (-11.11ε)…(4)

[0105] The compactibility index Ic is an index using a formula of Ryshkewitch-Duckworth (the following formula (5)) generally used for a relation between strength and a void structure of a brittle porous material. k is a constant derived from an experiment and indicates an adhesion (bonding capacity) of an original material.

[0106] σ = Ic・exp (-kε)…(5)

[0107] The compactibility index Ic indicates an absolute value of the tensile strength σ with respect to a graph of the compactibility having substantially the same slope as in Fig. 6. Here, the compactibility index Ic indicates the compactibility, but can also be a measure indicating solubility (porosity) and manufacturability (strength) itself of a product.

[0108] For example, when the porosity of the solid milk is less than 30%, the solubility of the product is significantly reduced. In addition, when the strength (tensile strength) of the solid milk is less than 45 kPa, the manufacturability is significantly reduced, for example, the product cannot be conveyed, and industrial production becomes difficult. Therefore, the compactibility index Ic is preferably, for example, 1.3 (MPa) or more (strength (tensile strength) at porosity of 30% is 46.4 kPa).

[0109] Fig. 7 shows a relation between the compactibility index Ic and the average sphericity Φave calculated based on the results in Fig. 6. In Fig. 7, filled circles shown in a region indicated by dots represent the powdered milk 1 of Examples 4 to 9 in which the average sphericity Φave is 0.66 or less. Based on results in Fig. 7, it is clear that powdered milk having a low average sphericity Φave has high compactibility. It was confirmed that the compactibility of Examples 4 to 9 was improved as compared with Comparative Examples 2 to 16, which are general powdered milk. Based on the results in Fig. 7, it was confirmed that the average sphericity Φave is preferably 0.66 or less and the compactibility index Ic is preferably 1.3 (MPa) or more.

[0110] (4) Operation and Effects As described above, it is possible to provide powdered milk 1 having excellent compactibility when the average sphericity Φave of the powdered milk 1 according to the present embodiment is set to 0.66 or less. In addition, the powdered milk 1 preferably has a particle density of 1.16 (g / cm3) or less, and accordingly, the compactibility can be further improved.

[0111] In the method for measuring the average sphericity Φave of the powdered milk 1 according to the present embodiment, a three-dimensional image obtained by imaging each particle constituting the powdered milk 1 is acquired (image acquisition step), and a three-dimensional model of the particle constituting the powdered milk 1 is created based on the three-dimensional image (three-dimensional model creation step). After the three-dimensional model creation step, the average sphericity Φave of the powdered milk 1 is calculated based on the three-dimensional model of the particle constituting the powdered milk 1 (average sphericity calculation step). It is desired to further include, before the three-dimensional model creation step, a threshold value correction step of adjusting a binarization threshold value and an internal void removing step of removing an internal void of a particle in a binarized image generated based on the three-dimensional image. Accordingly, the method for measuring the average sphericity Φave of the powdered milk 1 can perform shape analysis of the powdered milk 1 in which fine particles are aggregated. Further, when the internal void removing step is performed, it is desired to perform a void volume correction step of adjusting the maximum internal void volume v3 which is a reference when the internal void is removed. Accordingly, a three-dimensional model in which a shape of each particle is accurately reproduced can be created based on the binarized image generated based on the three-dimensional image.

[0112] (5) Method for Measuring Average Sphericity of Powder Regarding the procedure of the average sphericity calculation process in the above-described "(1-3) Average Sphericity", the case where the average sphericity Φave of the powdered milk 1 is measured has been described as an example, but the present invention is not limited to the powdered milk. The powder for which the average sphericity Φave is measured may be, for example, food powder or powder of such as medicine, mineral, building material, or resin. In an embodiment in which the average sphericity Φave of powder other than the powdered milk is measured, the " powdered milk" may be understood as "food powder" or "powder" in the above-described "(1-3) Average Sphericity".

[0113] As the food powder for which the average sphericity Φave can be measured by the procedure of the average sphericity calculation process, for example, protein powder such as whey protein, soybean protein, and collagen peptide, amino acid powder, and oil and fat-containing powder such as MCT oil can be used in addition to the powdered milk. Lactose or other sugars may be appropriately added to the food powder. In addition to lactose or other sugars, food additives and nutritional components such as fat, protein, minerals, and vitamins may be added to the food powder.

[0114] Further, the protein powder of the food powder may be milk casein, meat powder, fish powder, egg powder, wheat protein, wheat protein degradation product, or the like. These protein powder may be used alone or in combination of two or more kinds thereof.

[0115] Further, the whey protein of the food powder is a generic term for protein in milk excluding casein. The protein may be classified as whey protein. The whey protein is composed of a plurality of components such as lactoglobulin, lactalbumin, and lactoferrin. When a milk raw material such as milk is adjusted to be acidic, protein that precipitates is casein, and protein that does not precipitate is whey protein. Examples of a powder raw material containing whey protein include whey protein concentrate (WPC, protein content: 75 (mass%) to 85 (mass%)) and whey protein isolate (WPI, protein content: 85 (mass%) or more). These may be used alone or in combination of two or more kinds thereof.

[0116] Further, the soybean protein of the food powder may be protein contained in soybeans, and may be protein extracted from soybeans. In addition, protein purified from raw material soybeans can also be used. A purification method is not particularly limited, and a method known in the related art can be used. As such soybean protein, powder commercially available as materials for food and drink, medical materials, and supplement food can be used. These may be used alone or in combination of two or more kinds thereof.

[0117] Further, an amino acid contained in the amino acid powder of the food powder is not particularly limited, and examples thereof may include arginine, lysine, ornithine, phenylalanine, tyrosine, valine, methionine, leucine, isoleucine, tryptophan, histidine, proline, cysteine, glutamic acid, asparagine, aspartic acid, serine, glutamine, citrulline, creatine, methyllysine, acetyl lysine, hydroxylysine, hydroxyproline, glycine, alanine, threonine, and cystine. These may be used alone or in combination of two or more kinds thereof.

[0118] The amino acid contained in the amino acid powder of the food powder may be either a natural product or a synthetic product, and a single amino acid or a mixture of a plurality of amino acids can be used. As the amino acid, not only free amino acids but also salts such as sodium salt, hydrochloride, and acetate, and derivatives such as carnitine and ornithine can be used.

[0119] In the present description, the "amino acid" includes α-amino acid, β-amino acid, and γ-amino acid. In addition, the amino acid may be either an L-form or a D-form.

[0120] Further, oils and fats contained in the oil and fat-containing powder of the food powder are animal oil and fat, vegetable oil and fat, fractionated oil thereof, hydrogenated oil, and transesterified oil in addition to the above-described MCT oil. One or two or more of these may be added. Examples of the animal oil and fat include milk fat, lard, beef tallow, and fish oil. Examples of the vegetable oil and fat include soybean oil, rapeseed oil, corn oil, coconut oil, palm oil, palm kernel oil, safflower oil, cottonseed oil, linseed oil, and medium chain triglyceride (MCT, medium chain fatty acid triglyceride) oil.

[0121] Further, examples of the sugar of the food powder include, in addition to the above-described lactose, oligosaccharides, monosaccharides, polysaccharides, and artificial sweeteners. One or two or more of these may be added. Examples of the oligosaccharide include lactose, sucrose, maltose, galactooligosaccharide, fructooligosaccharide, and lactulose. Examples of the monosaccharide include glucose, fructose, and galactose. Examples of the polysaccharide include starch, soluble polysaccharides, and dextrin.

[0122] Further, a sweetener is exemplified as an example of the food additives of the food powder. As the sweetener, any sweetener commonly used for food and pharmaceutical products can be used, and any of natural sweeteners and synthetic sweeteners may be used. The sweetener is not particularly limited, and examples thereof include glucose, fructose, maltose, sucrose, oligosaccharide, sugar, granulated sugar, maple syrup, honey, molasses, trehalose, palatinose, maltitol, xylitol, sorbitol, glycerin, aspartame, advantame, neotame, sucralose, acesulfame potassium, and saccharin.

[0123] Further, an acidulant is exemplified as an example of the food additives of the food powder. The acidulant is not particularly limited, and examples thereof include acetic acid, citric acid, anhydrous citric acid, adipic acid, succinic acid, lactic acid, malic acid, phosphoric acid, gluconic acid, tartaric acid, and salts thereof. The acidulant can prevent (mask) bitterness that occurs depending on a type of the amino acid.

[0124] Further, the nutritional component of the food powder may contain any component such as fat, protein, mineral, and vitamin.

[0125] Examples of the fat include animal oil and fat, vegetable oil and fat, fractionated oil thereof, hydrogenated oil, and transesterified oil. One or two or more of these may be added. Examples of the animal oil and fat include milk fat, lard, beef tallow, and fish oil. Examples of the vegetable oil and fat include soybean oil, rapeseed oil, corn oil, coconut oil, palm oil, palm kernel oil, safflower oil, cottonseed oil, linseed oil, and medium chain triglyceride (MCT, medium chain fatty acid triglyceride) oil.

[0126] Examples of the protein include milk protein, milk protein fraction, animal protein, vegetable protein, and peptides and amino acids obtained by degrading these protein into various chain lengths with an enzyme or the like. One or two or more of these may be added. Examples of the milk protein include casein, whey protein (α-lactalbumin, β-lactoglobulin, and the like), whey protein concentrate (WPC), and whey protein isolate (WPI). Examples of the animal protein include egg protein (egg powder), meat powder, and fish powder. Examples of the vegetable protein include soybean protein and wheat protein. The peptide is, for example, a collagen peptide. Examples of the amino acid include taurine, cystine, cysteine, arginine, and glutamine. One or two or more of these may be added.

[0127] Examples of the mineral include iron, sodium, potassium, calcium, magnesium, phosphorus, chlorine, zinc, iron, copper, and selenium. One or two or more of these may be added.

[0128] Examples of the vitamin include vitamin A, vitamin D, vitamin E, vitamin K, vitamin B1, vitamin B2, vitamin B6, vitamin B12, vitamin C, niacin, folate, pantothenic acid, and biotin. One or two or more of these may be added.

[0129] Examples of other food materials include cocoa powder, cacao powder, chocolate powder, microorganism powder containing useful microorganisms such as lactic acid bacteria and bifidobacteria, milk fermented component powder in which a culture obtained by adding microorganisms to milk and fermenting the milk is used as powder, cheese powder in which cheese is used as powder, functional food powder in which functional food is used as powder, and a comprehensive nutritional food powder in which comprehensive nutritional food is used as powder. One or two or more of these may be added.

[0130] As described above, also in the method for measuring the average sphericity Φave of the powder, a three-dimensional image obtained by imaging each particle constituting the powder is acquired (image acquisition step), and a three-dimensional model of the particle constituting the powder is created based on the three-dimensional image (three-dimensional model creation step). In the method for measuring the average sphericity Φave of the powder, the average sphericity Φave of the powder is calculated based on the three-dimensional model of the particle constituting the powder (average sphericity calculation step). In the same manner as in the above-described embodiment, it is desired to further include, before the three-dimensional model creation step, a threshold value correction step, an internal void removing step, and a void volume correction step. Accordingly, in the method for measuring the average sphericity Φave of the powder, shape analysis of the powder in which fine particles are aggregated can be performed.

[0131] <Aspects> (Aspect 1) A powdered milk having average sphericity of 0.66 or less. (Aspect 2) The powdered milk according to aspect 1, which is used as a raw material of solid milk manufactured by compression molding. (Aspect 3) The powdered milk according to aspect 1 or 2, in which an average particle density is 1.16 [g / cm3] or less. (Aspect 4) A method for manufacturing solid milk, including: a compression step of compression molding the powdered milk according to any of aspects 1 to 3. (Aspect 5) The method for manufacturing solid milk according to aspect 4, further including: a powdered milk manufacturing step of manufacturing the powdered milk before the compression step, in which the powdered milk manufacturing step includes a drying step of spray drying liquid milk as a raw material of the powdered milk. (Aspect 6) The method for manufacturing solid milk according to aspect 4, further including: a powdered milk manufacturing step of manufacturing the powdered milk before the compression step, in which the powdered milk manufacturing step includes a granulation step of mixing fine particles with each other to bind a plurality of fine particles, and the powdered milk is manufactured by the granulation step. (Aspect 7) The method for manufacturing solid milk according to aspect 6, in which in the granulation step, the powdered milk is generated by mixing the fine particles with each other to bind the plurality of fine particles using a liquid. (Aspect 8) Solid milk manufactured by the manufacturing method according to any of aspects 4 to 7, in which tensile strength is 90 [kPa] or more. (Aspect 9) Solid milk manufactured by the manufacturing method according to any of aspects 4 to 7, in which porosity is 30 [%] or more. (Aspect 10) A method for measuring average sphericity of powder, including: an image acquisition step of acquiring a three-dimensional image obtained by imaging each particle constituting the powder; a three-dimensional model creation step of creating a three-dimensional model of the particle constituting the powder based on the three-dimensional image; an average sphericity calculation step of calculating average sphericity of the powder based on the three-dimensional model of the particle constituting the powder. (Aspect 11) The method for measuring average sphericity of powder according to aspect 10, further including: an internal void removing step of removing an internal void of the particle in a binarized image generated based on the three-dimensional image, in which in the three-dimensional model creation step, the three-dimensional model is created based on the binarized image generated based on the three-dimensional image. Reference Sign List

[0132] 1 powdered milk (powder)

Claims

A powdered milk having average sphericity of 0.66 or less.The powdered milk according to claim 1, which is used as a raw material of solid milk manufactured by compression molding.The powdered milk according to claim 1, whereinan average particle density is 1.16 [g / cm3] or less.A method for manufacturing solid milk, comprising:a compression step of compression molding the powdered milk according to claim 1.The method for manufacturing solid milk according to claim 4, further comprising:a powdered milk manufacturing step of manufacturing the powdered milk before the compression step, whereinthe powdered milk manufacturing step includes a drying step of spray drying liquid milk as a raw material of the powdered milk.The method for manufacturing solid milk according to claim 4, further comprising:a powdered milk manufacturing step of manufacturing the powdered milk before the compression step, whereinthe powdered milk manufacturing step includesa granulation step of mixing fine particles with each other to bind a plurality of fine particles, andthe powdered milk is manufactured by the granulation step.The method for manufacturing solid milk according to claim 6, whereinin the granulation step,the powdered milk is generated by mixing the fine particles with each other to bind the plurality of fine particles using a liquid.Solid milk manufactured by the manufacturing method according to any of claims 4 to 7, whereintensile strength is 90 [kPa] or more.Solid milk manufactured by the manufacturing method according to any of claims 4 to 7, whereinporosity is 30 [%] or more.A method for measuring average sphericity of powder, comprising:an image acquisition step of acquiring a three-dimensional image obtained by imaging each particle constituting the powder;a three-dimensional model creation step of creating a three-dimensional model of the each particle constituting the powder based on the three-dimensional image; andan average sphericity calculation step of calculating average sphericity of the powder based on the three-dimensional model of the each particle constituting the powder.The method for measuring average sphericity of powder according to claim 10, further comprising:an internal void removing step of removing an internal void of the particle in a binarized image generated based on the three-dimensional image, whereinin the three-dimensional model creation step, the three-dimensional model is created based on the binarized image generated based on the three-dimensional image.

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